Complexity_ A Guided Tour - Melanie Mitchell [35]
Pre-Darwinian Notions of Evolution
The word evolution means “gradual change.” Biological evolution is the process of gradual (and sometimes rapid) change in biological forms over the history of life. Until the eighteenth century, the prevailing opinion was that biological forms do not change over time; rather, all organisms were created by a deity and have largely remained in their original form since their creation. Although some ancient Greek and Indian philosophers had proposed that humans arose via transmutation from other species, in the West the conception of divine creation began to be widely questioned only in the eighteenth century.
In the mid-1700s, 100 years before Darwin proposed his theory, a French zoologist named George Louis Leclerc de Buffon published a many-volume work entitled Historie Naturelle, in which he described the similarities between different species. Buffon suggested that the earth is much older than the Biblical 6,000 years and that all modern organisms evolved from a single ancestor, though he did not propose a mechanism for this evolution. Buffon’s work in biology and geology was a significant break from the prevailing creationist viewpoint. Not surprising, the Catholic Church in France burned copies of his books.
Charles Darwin’s grandfather, Erasmus Darwin, was another prominent eighteenth-century scientist who believed in the evolution of all species from a single ancient ancestor. He proposed mechanisms for evolution that were precursors to his grandson’s theory of natural selection. Erasmus Darwin expressed his ideas both in scientific writing and in poetry:
Organic life beneath the shoreless waves
Was born and nurs’d in ocean’s pearly caves;
First forms minute, unseen by spheric glass,
Move on the mud, or pierce the watery mass;
These, as successive generations bloom,
New powers acquire and larger limbs assume;
Whence countless groups of vegetation spring,
And breathing realms of fin and feet and wing.
If only modern-day scientists were so eloquent! However, like the Catholics in France, the Anglican Church didn’t much like these ideas.
The most famous pre-Darwinian evolutionist is Jean-Baptiste Lamarck. A French aristocrat and botanist, Lamarck published a book in 1809, Philosophie Zoologique, in which he proposed his theory of evolution: new types of organisms are spontaneously generated from inanimate matter, and these species evolve via the “inheritance of acquired characteristics.” The idea was that organisms adapted to their environment during their lifetimes, and that these acquired adaptations were then passed directly to the organisms’ offspring. One example in Lamarck’s book was the acquisition of long legs by wading birds, such as storks. Such birds, he believed, originally had to stretch their legs in order to keep their bodies out of the water. This continual stretching made their legs longer, and the acquired trait of longer legs was passed on to the birds’ offspring, who stretched their legs even longer, passing this trait on to their own offspring, and so on. The result is the very long legs we now see on wading birds.
Lamarck gave many other such examples. He also asserted that evolution entails a “tendency to progression,” in which organisms evolve to be increasingly “advanced,” with humans at the pinnacle of this process. Thus, changes in organisms are predominately changes for the better, or at least, for the more complex.
Lamarck’s ideas were rejected by almost all of his contemporaries—not only by proponents of divine creation but also by people who believed in evolution. The evolutionists were not at all convinced by Lamarck’s examples of evolution via inheritance of acquired characteristics, and indeed, his empirical data were weak and were generally limited to his own speculations on how certain